排序方式: 共有12条查询结果,搜索用时 15 毫秒
1.
Modelling the thermal behaviour of carboxylic acid derivatives with cylcodextrins in the solid-state
Agotonovic-Kustrin S. Glass B. D. Brown M. E. Rotich M. K. 《Journal of Thermal Analysis and Calorimetry》2004,77(2):391-402
The application of classical QSAR and molecular modelling to the inclusion complexation of natural and modified cyclodextrins
(CDs) with carboxylic acid derivatives as guest molecules was examined. Information was available on the thermal behaviour,
in the solid-state of benzoic acid (BA), salicylic acid (SA), and various substituted aminosalicylic acids (3-aminosalicylic
acid, 3-ASA, 4-aminosalicylic acid, 4-ASA and 5-aminosalicylic acid, 5-ASA), as well as on the thermal behaviour of 1:1 molar
ratio physical and kneaded mixtures of these acids with each of three different cyclodextrins, β-, (BCD) 2-hydroxypropyl-β-,
(HPBCD) and γ-cyclodextrin (GCD). The thermal behaviour of the binary (1:1 stoichiometry) mixtures was modelled using stepwise
multiple regression (SMR). Two models for the prediction of the percentage mass loss and enthalpy of dehydration of the physical
mixtures were established with correlation coefficients (r) of 0.79 and 0.92, respectively. Decreased correlation in the thermal behaviour of kneaded mixtures indicated significant
interaction and possible formation of inclusion complexes.
This revised version was published online in July 2006 with corrections to the Cover Date. 相似文献
2.
高效液相色谱法分离和测定面粉中增白剂过氧化苯甲酰 总被引:22,自引:0,他引:22
提出了用高效液相色谱分离和测定面粉中增白剂过氧化苯甲酰的新方法。用乙醇为熔剂通过超声提取面粉中的过氧化苯甲酰,在氢氧化钾存在下使之转化为苯甲酸,再用HPLC进行测定,具有良好的准确度和再现性。 相似文献
3.
Rotich A. Benson Nader M. A. Mohamed Mohamed Soliman Mohammed Hassan Mohsen A. Abou Mandour 《Journal of Radioanalytical and Nuclear Chemistry》2017,311(1):23-27
Rapid determination of gross alpha and beta emitters in urine by liquid scintillation counting is discussed. This method is based on direct addition of urine into scintillation cocktail. 241Am, 239Pu and 90Sr were selected as model radionuclides. The LSA Hidex 300 SL equipped with Triple-Double-Coincidence-Ratio technique was used for sample measurement. The work focused on optimizing the LSC cocktail to urine volume ratio with respect to the model radionuclides. The overall efficiencies for 241Am, 239Pu and 90Sr were greater than 92 %; therefore, this method would be suitable for rapid determination of gross alpha/beta activity. 相似文献
4.
排序问题中优化准则关于基本参数的正则性及其应用 总被引:1,自引:0,他引:1
本文提出了优化准则关于加工时间、准备时间、应交工时间的正则性,利用这种正则性对寻找参数可控排序问题中的有效值、有效解给出了一直观算法,并指出对一些具体的参数可控排序问题,其有效值、有效解的寻找可通过对这一直观算法加以具体化而得.文中还对平均流程问题给出了这样一个具体化算法. 相似文献
5.
M. K. Rotich B. D. Glass M. E. Brown 《Journal of Thermal Analysis and Calorimetry》2001,64(2):681-688
The thermal behaviour of various substituted aminobenzoic acids(3-aminobenzoic acid (3-ABA), 4-aminobenzoic acid (4-ABA),
3-aminosalicylic acid(3-ASA), 4-aminosalicylic acid (4-ASA), and 5-aminosalicylic acid (5-ASA), as well as the‘parent’ benzoic
acid (BA) and salicylic acid (SA) as reference substances, and possible decomposition products: 2-aminophenol (2-AP), 3-aminophenol
(3-AP) and 4-aminophenol(4-AP) in the solid state has been examined.
The various sets of isomers studied showed considerable and interesting differences. Most sublimed well before melting, generally
with an increasing rate of mass loss beyond their very different melting points. The differences in behaviour of 4-ASA and
5-ASA were the most remarkable, with 5-ASA being far more stable and apparently not decarboxylating readily, while 4-ASA sublimed
at temperatures below the melting point, becoming less stable and decarboxylating in the liquid form.
This revised version was published online in July 2006 with corrections to the Cover Date. 相似文献
6.
Rotich M. K. Brown M. E. Glass B. D. 《Journal of Thermal Analysis and Calorimetry》2003,73(2):671-686
The thermal behaviour of benzoic and salicylic acids is compared with the behaviour of 1:1 molar ratio physical and kneaded
mixtures of these acids with each of three different cyclodextrins (b-, hydroxypropyl-b-, and g-cyclodextrin). Differential
scanning calorimetry and thermogravimetry coupled with evolved gas analysis by Fourier transform infrared spectroscopy were
used for the thermal studies and X-ray powder diffraction and infrared spectroscopy provided complementary information. Thermal
studies of benzoic acid with the cyclodextrins showed significant interactions in both physical and kneaded mixtures of benzoic
acid/b-cyclodextrin and benzoic acid/hydroxypropyl-b-cyclodextrin. Interactions in the kneaded benzoic acid/g-cyclodextrin
mixtures were the most extensive as might be expected for the cyclodextrin with the largest molecular cavity. The results
for the salicylic acid/b-cyclodextrin and salicylic acid/hydroxypropyl-b-cyclodextrin mixtures were similar to those for benzoic
acid/b-cyclodextrin and benzoic acid/hydroxypropyl-b-cyclodextrin. Again, the kneaded salicylic acid/g-cyclodextrin mixture
showed the most interaction.
This revised version was published online in July 2006 with corrections to the Cover Date. 相似文献
7.
Henry K. Rotich Zhuoyong Zhang Jinchang Li 《International journal of environmental analytical chemistry》2013,93(10):851-860
High-performance liquid chromatography with solid-phase extraction (HPLC-SPE) was optimized for the analysis of three organophosphorus pesticide residues in water, apples and vegetable samples. Octadecylsilica disks (47-mm diameter) were used for solid-phase extraction. The parameters that affect both separation and extraction of methyl parathion, parathion and phoxim, such as mobile-phase composition, ionic strength, temperature, pH, and breakthrough volume, were investigated. The application of optimized HPLC-SPE to environmental samples gave reproducible results with low detection limits of 5 µg L?1 for methyl parathion and parathion and 2.5 µgL?1. Precisions of less than 8, 9 and 12% were obtained for water, spinach and apple samples, respectively. 相似文献
8.
Journal of Thermal Analysis and Calorimetry - As the global temperature increases over time due to different environmental pollutions, apparel clothing with excellent thermo-physiological comfort... 相似文献
9.
高效液相色谱法和固相萃取法用于环境中农药残留物分析的研究进展 总被引:9,自引:0,他引:9
农药是一类被广泛使用的毒药 ,由于它们在现代农业中的广泛使用及其毒性 ,越来越引起人们对水、食品、农产品以及环境中的农药残留分析的重视 ,高效液相色谱法 (HPLC)和固相萃取法 (SPE)由于其具有分析速度快、灵敏度高的特点 ,特别适合于农药残留物分析 .本文对近年来用于环境中农药残留物的分析和有关的研究进展做了较全面的评述 相似文献
10.
LiMin Jin Yao Yao YiMin Yu Gideon Rotich BaoZhong Sun BoHong Gu 《中国科学:物理学 力学 天文学(英文版)》2014,57(3):501-511
This paper reports the structural effects of three-dimensional (3-D) angle-interlock woven composite (3DAWC) undergoing three-point bending cyclic loading from experimental and finite element analysis (FEA) approaches. In experiment, the fatigue tests were conducted to measure the bending deflection and to observe the damage morphologies. By the FEA approach, a micro-structural unit-cell model of the 3DAWC was established at the yarn level to simulate the fatigue damage. The stress degradation at the loading condition of constant deformation amplitude was calculated to show the degradation of mechanical properties. In addition, the stress distribution, fatigue damage evolution and critical damage regions were also obtained to qualitatively reveal the structural effects and damage mechanisms of the 3DAWC subjected to three-point bending cyclic loading. 相似文献